Prism.languages.c = Prism.languages.extend('clike', {
    'comment': {
        pattern: /\/\/(?:[^\r\n\\]|\\(?:\r\n?|\n|(?![\r\n])))*|\/\*[\s\S]*?(?:\*\/|$)/,
        greedy: true
    },
    'string': {
        // https://en.cppreference.com/w/c/language/string_literal
        pattern: /"(?:\\(?:\r\n|[\s\S])|[^"\\\r\n])*"/,
        greedy: true
    },
    'class-name': {
        pattern: /(\b(?:enum|struct)\s+(?:__attribute__\s*\(\([\s\S]*?\)\)\s*)?)\w+|\b[a-z]\w*_t\b/,
        lookbehind: true
    },
    'keyword': /\b(?:_Alignas|_Alignof|_Atomic|_Bool|_Complex|_Generic|_Imaginary|_Noreturn|_Static_assert|_Thread_local|__attribute__|asm|auto|break|case|char|const|continue|default|do|double|else|enum|extern|float|for|goto|if|inline|int|long|register|return|short|signed|sizeof|static|struct|switch|typedef|typeof|union|unsigned|void|volatile|while)\b/,
    'function': /\b[a-z_]\w*(?=\s*\()/i,
    'number': /(?:\b0x(?:[\da-f]+(?:\.[\da-f]*)?|\.[\da-f]+)(?:p[+-]?\d+)?|(?:\b\d+(?:\.\d*)?|\B\.\d+)(?:e[+-]?\d+)?)[ful]{0,4}/i,
    'operator': />>=?|<<=?|->|([-+&|:])\1|[?:~]|[-+*/%&|^!=<>]=?/
});

Prism.languages.insertBefore('c', 'string', {
    'char': {
        // https://en.cppreference.com/w/c/language/character_constant
        pattern: /'(?:\\(?:\r\n|[\s\S])|[^'\\\r\n]){0,32}'/,
        greedy: true
    }
});

Prism.languages.insertBefore('c', 'string', {
    'macro': {
        // allow for multiline macro definitions
        // spaces after the # character compile fine with gcc
        pattern: /(^[\t ]*)#\s*[a-z](?:[^\r\n\\/]|\/(?!\*)|\/\*(?:[^*]|\*(?!\/))*\*\/|\\(?:\r\n|[\s\S]))*/im,
        lookbehind: true,
        greedy: true,
        alias: 'property',
        inside: {
            'string': [
                {
                    // highlight the path of the include statement as a string
                    pattern: /^(#\s*include\s*)<[^>]+>/,
                    lookbehind: true
                },
                Prism.languages.c['string']
            ],
            'char': Prism.languages.c['char'],
            'comment': Prism.languages.c['comment'],
            'macro-name': [
                {
                    pattern: /(^#\s*define\s+)\w+\b(?!\()/i,
                    lookbehind: true
                },
                {
                    pattern: /(^#\s*define\s+)\w+\b(?=\()/i,
                    lookbehind: true,
                    alias: 'function'
                }
            ],
            // highlight macro directives as keywords
            'directive': {
                pattern: /^(#\s*)[a-z]+/,
                lookbehind: true,
                alias: 'keyword'
            },
            'directive-hash': /^#/,
            'punctuation': /##|\\(?=[\r\n])/,
            'expression': {
                pattern: /\S[\s\S]*/,
                inside: Prism.languages.c
            }
        }
    }
});

Prism.languages.insertBefore('c', 'function', {
    // highlight predefined macros as constants
    'constant': /\b(?:EOF|NULL|SEEK_CUR|SEEK_END|SEEK_SET|__DATE__|__FILE__|__LINE__|__TIMESTAMP__|__TIME__|__func__|stderr|stdin|stdout)\b/
});

delete Prism.languages.c['boolean'];